Trends in incidence of primary malignant brain tumors in USA, 1981-1990

There has been considerable controversy regarding whether a recent observed rise in brain tumor incidence is real and so suggestive of increasing exposure to environmental carcinogens, or whether it is largely explainable by changes in diagnostic technology, particularly the introduction of computerized axial tomography (CT) scans in the 1970s. We analysed data from the US Surveillance, Epidemiology, and End Results (SEER) Program to investigate whether there was a rise of brain tumor incidence during 1981-1990, the period after CT scans became extensively available, and if so, the rates of which specific histologic subtypes have risen.

Age- and sex-specific, as well as age-adjusted incidence rates were calculated for each brain tumor histologic subtype. Regression analysis was used to estimate age-adjusted incidence rate ratios (RR) for different periods and to examine time trends.

For all histologic subtypes, the incidence rates increased with age. Regarding time trends, lymphomas in men increased in all age groups during the study period with the age-adjusted rate ratio reaching 5.6 (95% CI: 3.7-8.3) for 1989-1990 as compared to 1981-1982. Lymphoma in women and glioblastoma multiforme in both sexes also appear to have increased, particularly in the elderly. Other histologies did not show any time trends in the age-specific or age-adjusted analyses.

Our histology-specific analysis is not suggestive of any significant increase in the incidence of brain tumors during 1980-1990, except for lymphomas in men.